book

Head First Git

by Raju Gandhi

January 2022

Beginner

508 pages

12h 43m

English

O'Reilly Media, Inc.

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Who is this book for?Who should probably back away from this book?We know what you’re thinkingWe know what your brain is thinkingThis must be important! Don’t forget it!Metacognition: thinking about thinkingSo just how DO you get your brain to treat Git like it’s a hungry tiger?Here’s what WE didHere’s what YOU can do to bend your brain into submissionRead meWe break things down, then build them back again.We don’t exhaustively cover everything.The activities are NOT optional.The redundancy is intentional and important.The examples are as generic as possible.The Brain Power exercises don’t have answers.Not all Test Drive exercises have answers.You’re going to have to install Git (macOS)Using the terminal to verify the installationYou’re going to have to install Git (Windows)Using Git Bash to verify the installationYou’re going to need a text editor (macOS)You’re going to need a text editor (Windows)You’re (definitely) going to need a GitHub accountSetting up a personal access tokenA word on organizing your files and projectsThe technical review teamO’Reilly Online LearningAcknowledgmentsJust when you thought there wouldn’t be any more acknowledgments*
Why we need version controlCubicle ConversationGot Git?Start your engines...A quick tour of the command line: knowing where you are with pwdMore on the command line: creating new directories with mkdir(Even) More on the command line: listing files with IsMore on the command line (almost there): changing directories with cdNo argument thereCleaning upCreating your first repositoryInside the init commandCode MagnetsIntroduce yourself to GitHow you will use GitPutting Git to workMeanwhile, back at the HawtDog Dating Service...Working with the HawtDawg Git repositorySpeaking of...Congratulations on your first commit!What exactly does it mean to commit?Look before you leapThe three stages of GitGreat question!Git in the command lineA peek behind the curtainThe multiple states of files in a Git repositoryA typical day in the life of a new fileThe object database is the “source of truth”BE GitThe index is a “scratch pad”Computer, status report!Whoa, easy tiger!You’ve made history!Crossword InitCode Magnets SolutionBE Git SolutionCrossword Init Solution
It all started with an emailBut things didn’t quite pan out...What would you do if you were Norm?Updating the restaurant menuFirst things firstVery astute!Choices...so many choices!Switching tracksBack at the ’80s DinerSend it back!Code MagnetsVisualizing branchesBranches, commits, and the files contained withinBE GitCubicle ConversationWorking in parallelBE GitWhat is a branch, really?Switching branches, or switching directories?Some branches are more equal than othersBring it in!Read the #&$!@ manual (git branch edition)Making the fall menu officialSome merges are fast-forwardIt doesn’t quite work the other wayA little more Git setupIt’s almost Thursday!Wait! You moved?It’s almost Thursday! (continued)It’s a merge commitMerge commits are kinda specialThings don’t always go so smoothlyI am so conflicted!I am so conflicted! (Ooof! Almost there)Cleaning up (merged) branchesThe answer to your question lies in the commit history.Deleting unmerged branchesA typical workflowGit branch “crossword puzzle”Code Magnets SolutionBE Git SolutionBE Git SolutionGit branch “crossword puzzle” Solution
Brigitte’s on a missionCommits aren’t enoughMirror, mirror on the wall: who is the prettiest log of all?How does git log work?Making git log do all the workWhat diff-erence does it make?Visualizing file differencesVisualizing file differences: one file at a timeVisualizing file differences: one hunk at a timeMaking diffs easier on the eyesDiffing staged changesDiffing branchesDiffing branches (we are there!)Diffing commitsWhat does the diff for a new file look like?A Diff-icult CrosswordA Diff-icult Crossword Solution
Planning an engagement partyAn error in judgmentCubicle conversationUndoing changes to the working directoryUndoing changes in the indexDeleting files from Git repositoriesCommitting to deleteRenaming (or moving) filesEditing commit messagesAren’t you the observant one!Renaming branchesMaking alternative plansHEAD Tells AllThe role of HEADReferencing commits using HEADTraversing merge commitsUndoing commitsRemoving commits with resetThe three types of resetgit reset --softUsing git reset (or git reset --mixed)git reset --hardCongratulations, you time traveler, you!Another way to undo commitsReverting commitsAaaaand that’s a wrap!Undo CrosswordUndo Crossword Solution
Another way to a Git repository: cloningHosting a Git repositorySetting up: forking repositories (a sidebar)Ready, set, clone!It’s just another Git repositoryWhat happens when you clone?Git is distributedAnother bit of Git configurationPushing changesVerifying if the push workedKnowing where to push: remotesNo photographs, please: public versus private commitsPublic versus private commits (continued)Standard operating procedure: branchesMerging branches: option 1 (local merges)A quick note on GitHub’s interfacePushing local branchesMerging branches: option 2 (pull requests)Creating pull requestsCreating pull requests (Yep! Almost there)A brand-new, shiny pull requestPull requests or merge requests?Merging a pull requestWhat’s next?A Pushy PuzzleA Pushy Puzzle Solution
Cubicle conversationWorking in parallelWorking in parallel...in GitlandCubicle conversation (continued)Collaborating, Git styleThe setup for two collaborators on GitHubOur setup so farTwo-player setupOne-player setupCubicle conversation (continued)Falling behind the remoteCubicle conversation (continued)Catching up with the remote (git pull)Introducing the middlemen, aka remote tracking branchesReason 1 for remote tracking branches: knowing where to pushRemote tracking branch after you pushPushing to the remote: summaryFetching remote tracking branchesReason 2 for remote tracking branches: getting (all) updates from the remoteGit branch flag soupCubicle conversation (continued)Collaborating with othersGit push/pull and remote tracking branchesCollaborating with others: summaryReason 3 for remote tracking branches: knowing you need to pushReason 4 for remote tracking branches: getting ready to pushReason 4 (still going)Reason 4 (Yep! Almost there!)git pull is git fetch + git merge!Use git fetch + git merge. Avoid git pull.The ideal scenarioA typical workflow: getting startedA typical workflow: getting ready to mergeA typical workflow: merge locally, or issue pull requests?A typical workflow visualizedCleaning up remote branchesCollaborative CrosswordCollaborative Crossword Solution

Taking things to the next levelA walk through the commit historyCubicle conversationSeeing who changed what and when with git blameUsing git blamegit blame using Git repository managersA few more details about git blameSearching Git repositoriesSearching Git repositories with grepgit grep optionsCase-insensitive searchDisplaying line numbersList only filenamesThe git grep flags comboWhere git blame falls shortgit log’s “pickaxe” capability (-S)git log -S versus blameUsing the “patch” flag with git logUsing the “patch” flag with git log (almost there)git log’s other “pickaxe” flag (-G)Searching commit messagesGit log flag soupWhat does it mean to check out a commit?Checking out commitsDetached HEAD stateThe moral of the detached HEAD stateCubicle conversationSearching for commits using git bisectUsing git bisectFinishing git bisectSearching for CluesSearching for Clues Solution
Configuring GitThe global .gitconfig fileProject-specific Git configurationListing your Git configurationGit aliases, aka your personal Git shortcutsTweaking the behavior of Git aliasesTelling Git to ignore certain files and foldersThe effects of a .gitignore fileManaging the .gitignore fileA sample .gitignore fileCommit early, commit oftenWrite meaningful commit messagesThe anatomy of a good commit messageThe anatomy of a good commit message: headersCode MagnetsThe anatomy of a good commit message: bodiesFussy much?A shoutoutCreate helpful branch namesIntegrate a graphical user interface into your workflowThe command line versus a GUICongratulations!Configuration CrosswordCode Magnet SolutionConfiguration Crossword Solution
#1 Tags (remember me forever)#2 Cherry-pick (copying commits)#3 Stashes (pseudo-commits)#4 reflog (reference log)#5 rebase (another way to merge)This isn’t goodbye!

Content preview from Head First Git

Chapter 2. Branching Out: Multiple Trains of Thought

You can walk and chew gum at the same time. Git old-timers will tell you, as they recline in their lawn chairs (sipping their handcrafted green tea), that one of Git’s biggest selling points is the ease with which you can create branches. Perhaps you have been assigned a new feature, and while you are working on it, your manager asks you to fix a bug in production. Or maybe you just got around to putting the finishing touches on your latest change, but inspiration has struck and you’ve just thought of a better way of implementing it. Branches allow you to work on multiple, completely disconnected pieces of work on the same codebase at the same time, independently of one another. Let’s see how!

It all started with an email

Norm was completely immersed—his fingers flew frantically all over the keyboard, code appeared at a breathtaking pace on his screen, and everything just worked. He felt like Neo in the Matrix—he was the system, and the system was just an extension of him. He was so close to finishing up a complex change to the codebase that he could almost taste it.

Norm knew he wasn’t done yet. But he committed his code anyway, and he started to tackle the bug. At the end of a long day, when he knew he had fixed that ...